A reaserch scholar get a mixture of three product during an experimant with ammonia. In product `I` only one `H` of ammonia is replaced by ethyl group and in `II` two `H` atoms of ammonia are replaced by ethyl groups and in `III` alll the `H`-atoms are replaced by ethyl groups. Which test he should use to distinguish or separate the products :
A. Carbyl amine test
B. Iodoform test
C. Fehling solution test
D. Hinsberg test